(a) Field of the Invention
An exemplary embodiment of the present invention relates to a fastener element, and more particularly, to a rivet module for mechanically joining two or more sheets of base materials and a joining structure and method using the same.
(b) Description of the Related Art
In general, methods of forming a variety of structures by joining a plurality of base materials, for example, metal or non-metal plates, sheets, and randomly-shaped objects involve mechanically joining overlapping base materials by fastener elements such as bolts, nuts, rivets, etc.
Among them, the mechanical joining method using a rivet allows the fastening of base materials by making a hole in target base materials, inserting a rivet in the hole, and plastically deforming the rivet.
However, this joining method using a rivet requires an additional process of drilling a hole in the base materials, which may degrade productivity and workability.
To address this problem, those in the art have drifted toward the simple method of joining a plurality of base materials by a fastener element called an FDS (Flow Drill Screw). This fastener element is also referred to as a friction stir rivet.
In one example, an FDS rivet-type fastener element includes a head portion mounted on a pressure/rotation device, a screw portion integral with the head portion and having a thread on the outer peripheral surface, and a drilling portion integrally connected to the screw portion and for drilling through a base material.
Accordingly, in the joining method using the above-described fastener element, when the head portion is mounted on a pressure/rotation device and rotated under pressure by the pressure/rotation device, with the drilling portion being in contact with overlapping base materials, a hole is formed in the base materials by the friction between the drilling portion and the base materials and the base materials are fastened with the screw portion. Thus, the base materials are joined together.
Even with a joining structure obtained by joining base materials with such a fastener element, however, the quality of external appearance of joined products may be low because the screw portion and the drilling portion stick out from the base materials, and the joint strength of the base materials may be low because the base materials are joined in a solid state simply with the screw portion.
The above information disclosed in this section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.